In light of concerns about public health and safety, the development of touchless controls on bathroom and restroom fixtures has received a large amount of attention. Germs, bacteria, disease, and other harmful materials may be spread from one person to another by touching the handles on toilets, urinals, sinks, and other fixtures in public and private bathrooms.
A variety of touchless control systems have been developed. The most common type of touchless control employs an infrared or, less commonly, a visible light detector for sensing a user. The detector typically provides signals that open or close an actuator, such as a valve, attached to a water inlet conduit of the fixture to, for example, flush a toilet or cause a stream of water to flow out of a faucet Infrared radiation can be detected passively by sensing heat from a user. Alternatively, infrared light can be emitted by a device, such as a light emitting diode (LED), and reflected off a user to an infrared detector, such as a photocell.
The use of infrared detection has several limitations. First, infrared radiation cannot penetrate most materials because of the short wavelength of the radiation. Thus, infrared emitters and detectors are typically either exposed or are positioned behind a window made of material that is transparent to infrared radiation. In addition, infrared sensors can be inadvertently or purposefully blocked by some material, such as paper, dust, or cloth, in front of the emitter or detector.
Another disadvantage of infrared detection is that the reflectivity of objects, such as clothing, may vary widely. Thus, the infrared detector must be sensitive to a wide variation in the strength of reflected signals. There is a risk that the detector may fail to detect a user with clothing or other articles that absorb or only weakly reflect infrared radiation.
These disadvantages of infrared detectors may cause faulty responses by the fixture (e.g., flushing of a toilet at an inappropriate time or constant flow of water in a toilet or sink) or may result in a failure to operate until the sensor area is cleaned or blocking objects are removed. Thus, there is a need for a new type of detector that can overcome these deficiencies of current detectors.